Electrical conductor having inhibited polymer compositions

ABSTRACT

A polymeric composition having a polymer content which tends to evolve deleterious acid compounds upon being subjected to elevated temperatues; the composition including selected particle matter which is present in an amount to combine with or otherwise neutralize essentially the entire evolved deleterious compound when the composition is subjected to elevated temperatures; the composition with or without plasticizers being useful as insulation or jacketings for electric wire and cable, as well as diverse molded or extruded products, including disposable items such as packaging or the like.

This is a division of application Ser. No. 109,390, filed Jan. 25, 1971,and now U.S. Pat. No. 3,943,087, which is a continuation in part ofapplication Ser. No. 823,033, filed May 8, 1969.

BACKGROUND OF THE INVENTION

In many polymeric compositions used in the arts, the polymer componentthereof includes a functional group which upon being subjected toelevated temperatures, releases deleterious acid compounds into theatmosphere. Thus, for example, in the electrical industry, plasticizedpolyvinyl chloride is commonly used as an insulation or jacketing forelectrical cables or conductors; and at elevated temperatures, thechlorine content thereof is converted to gaseous hydrogen chloride. Thegaseous hydrogen chloride tends to extinguish any flames, and,consequently, the polyvinyl chloride compositions generally used forsuch applications, are flameproof. These compositions, however, aredisadvantageous in that the evolved hydrogen chloride will combine withwater or water vapor and corrode, destroy and/or impair any metal,masonry or other sensitive material in the vicinity of the evolvedcompounds.

These adverse effects are particularly serious in areas where highlysensitive metal elements such as switch contacts or other sensitivecontrol equipment is present. Further, in confined areas, the evolvedcorrosive compounds may be present in amounts sufficient to preventaccess to such areas for the purpose of extinguishing flames or thelike.

Many disposable consumer items, such as plastic containers and the like,include, for example, polyvinyl chloride; and such items upon beingdisposed of after use, as by incineration, release hydrogen chlorideinto the atmosphere, thereby further polluting the atmosphere.

An object of this invention is to provide polymer compositions which areinhibited against the release of deleterious compounds into theatmosphere, when the compositions are subjected to elevatedtemperatures, despite the presence in the composition of a deleteriousacid forming component.

Another object of this invention is to provide polyvinyl chloridecompositions which are formulated to prevent the release of hydrogenchloride into the atmosphere when the compositions are subjected toelevated temperatures.

A further object of this invention is to provide flameproof compositionswhich are inhibited to prevent the release of of deleterious acidcompounds into the surrounding atmosphere upon being subjected toelevated temperatures.

Still another object of this invention is to provide polymeric jacketingand insulating compositions for electrical cables or conductors, whichwill not release deleterious acid compounds into the surroundingatmosphere when such cables or conductors are subjected to elevatedtemperatures.

These and other objects of the present invention should be apparent tothose skilled in the art from reading the detailed description of theinvention, with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a longitudinal elevational view, with parts in section,showing an electrical conductor carrying a jacketing compositionemploying the invention; and

FIG. 2 is a transverse sectional view taken on the line 2--2 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The objects of this invention are broadly accomplished, in one aspect,by providing a polymer composition which includes a polymer which uponbeing subjected to an elevated temperature, evolves a deleterious acidiccompound; and a material which is capable of combining with thedeleterious acidic compound, the aforesaid material being present in anamount which is sufficient to combine with essentially all of thedeleterious acidic compound to thereby prevent any evolution of thedeleterious acidic compound in free form, into the surroundingatmosphere, when the composition is subjected to elevated temperatures.

More particularly, the polymer component of the composition, either as ahomopolymer or a copolymer, includes a functional group which isreleased as a deleterious acidic compound upon subjecting the polymer toan elevated temperature; such deleterious acidic compound being one ormore of the following: hydrogen bromide, hydrogen chloride, hydrogenfluoride, acetic acid and hydrogen cyanide.

As representative examples of polymers, which contain besides one ormore hydrogen atoms, either a cyano, chloro, bromo, acetoxy or cyanidegroup which is released as the corresponding acidic compound upon beingsubjected to an elevated temperature, there may be mentioned: polyvinylchloride, polyvinylidene chloride, polyvinyl acetate, polyvinylacetate-polyvinyl chloride copolymer, polychloroprene, chlorinatednatural and synthetic rubbers, chlorosulfonated polyethylene,chlorinated polyvinyl chloride, chlorinated polyethylene,polyacrylonitrile, acetylated cellulose, acrylonitrile-styrenecopolymer, acrylonitrile-butadiene, styrene copolymer, brominatedpolymers, polyvinyl fluoride, polyvinylidene fluoride, and copolymers ofvinylidene fluoride and perfluorinated olefins.

The material which is combined with the polymer is one which is capableof combining with the released acidic compound at the elevatedtemperature, to produce a compound which is non-deleterious at theelevated temperature, i.e., the resulting salt, at elevatedtemperatures, does not take the form of a deleterious material. Suchmaterials are generally one or more of the following: carbonates,oxides, hydroxides and oxalates of calcium, barium, magnesium andstrontium; carbonates of sodium and potassium; and the carbonate andoxide of lithium.

These materials react with the hereinabove described evolved deleteriousacid compounds to produce a salt of the acid, thereby preventing theacid compound from being released to the surrounding atmosphere. Formost applications, calcium carbonate is the preferred material in thelight of its ready availability and ease in processing.

The material is present in the composition in an amount which is atleast the stoichiometric quantity required to combine with essentiallyall of the deleterious acidic compound which could be released from thecomposition as a whole. The required stoichiometric amount of each ofthe materials may be readily calculated from the known amount of acidforming functional groups present in the polymer, and, therefore thestoichiometric amount of material required to insure essentially norelease of deleterious acidic acompound into the surrounding atmosphereis dependent on both the material selected and the specific polymercomponent of the composition.

In most cases, the composition includes an amount of material which isin excess of the calculated stoichiometric amount, in that, such excessamount is required to insure no evolution of deleterious acidic compoundinto the surrounding atmosphere. The minimum amount of material requiredvaries with the average particle size of the material; with materialshaving larger particle size requiring greater minimum stoichiometricexcesses to combine with essentially all of the evolved deleterious acidcompound. Stated in another way, the smaller the average particle sizeof the material, the closer the minimum amount of material required tocombine with essentially all of the evolved deleterious acidic compound,approaches the calculated stoichiometric amount of material.

For most applications, the average particle size of the material shouldnot exceed 250 millimicrons, and preferably not in excess of 100millimicrons. The selection of the minimum amount of material requiredto insure essentially no evolution of deleterious acidic compound foreach polymer and for each material is deemed to be within the scope ofthose skilled in the art, from the teachings herein. The following arerepresentative examples of various polymers and the calculatedstoichiometric amount of calcium carbonate required to insureessentially no evolution of deleterious acidic acompounds uponsubjecting the polymer composition to an elevated temperature.

    ______________________________________                                        Polymer             Calcium Carbonate                                         ______________________________________                                        polyvinyl chloride                                                                           100      80                                                    polychloroprene                                                                              100      56.5                                                  polyvinylidene 100      103                                                   chloride                                                                      polyvinyl fluoride                                                                           100      109                                                   all parts by weight                                                           ______________________________________                                    

The polymer composition may contain, in addition to the particlematerial which prevents evolution of deleterious acidic compounds intothe surrounding atmosphere; other components which are conventionallyincluded, as known in the art, such as plasticizers, stabilizers,colorants and the like, to provide the desired overall properties forthe composition; provided the composition includes a sufficient amountof the hereinabove noted particle materials to combine essentially allof the deleterious acidic compound released into the surroundingatmosphere upon subjecting the composition to an elevated temperature.

The compositions of the present invention have a wide variety ofapplications in that the compositions may be effectively employed foranyone of diverse applications presently known in the art, with theadded advantage that products formed from these compositions will notrelease deleterious acidic compounds into the surrounding atmosphereupon being subjected to elevated temperatures.

For Example, polymeric compositions including polyvinyl chloride arepresently employed as packages such as containers, trays, boxes and filmwrapping. These disposable packages upon being incinerated, releasehydrogen chloride into the atmosphere. By using the compositions of thepresent invention, which includes preferably calcium carbonateparticles; the incineration of such packages releases essentially nohydrogen chloride into the atmosphere, the hydrogen chloride being boundin the ash.

Thus, when using calcium carbonate as the particle material of thecomposition, the hydrogen chloride which would have been released to thesurrounding atmosphere, is converted to calcium chloride. The polyvinylchloride composition is made up of a polyvinyl chloride which providesthe desired mechanical properties, and the selected particle material.Such a composition may comprise by weight, 100 parts of polyvinylchloride having a K value of from 50 to 75, and 100 or more parts ofcalcium carbonate having an average particle size of about 50millimicrons. Articles made from such composition, after use, may beincinerated without the release of hydrogen chloride into thesurrounding atmosphere.

There are many other applications for which compositions which includepolymers of the type hereinabove described, should preferably notrelease deleterious acid compounds upon being subjected to elevatedtemperatures. For example, machinery and transport belts which are usedin mines, factories and the like, upon being subjected to elevatedtemperatures as in the case of fire; present an additional hazardbecause of the release of deleterious acidic compounds of the typehereinabove described. The use of compositions of the instant inventionfor such belts, will eliminate the hazard.

Similarly, a wide variety of non-flammable or slow burning compositions,generally formed of polyvinyl chloride, may be improved in accordancewith the teachings of the instant invention, by eliminating theadditional hazard to men and materials presented by the release ofhydrogen chloride incident to subjecting such compositions to elevatedtemperatures, as in a fire.

Thus, as should be apparent, the present invention is generallyapplicable to polymer compositions which include a polymer having afunctional group which will be released in the form of a deleteriousacidic compound, when the composition is subjected to elevatedtemperatures, as in the case of a fire or the like.

In the case of polyvinyl chloride, such elevated temperatures are inexcess of 200° C. The temperatures at which various other polymersrelease deleterious acidic compounds are known in the art and thereforeno detailed description in this respect is required.

The present invention is particularly suitable for the production ofinsulation or jackets for electrical conductors or cables; the samebeing derived from polyvinyl chloride which is suitable for bothinsulation and jackets; or polychloroprene which is used as a jacketingmaterial. The polyvinyl chloride and polychloroprene used for suchapplications, generally are plasticized to provide desired mechanicalproperties. Although such plasticized compositions areself-extinguishing; these compositions at elevated temperatures arisingfrom a fire or the like, release hydrogen chloride into the surroundingatmosphere.

In accordance with the instant invention, polyvinyl chloride orpolychloroprene; and in particular, polyvinyl chloride, is combined witha non-flammable plasticizer, together with a particle material of thetype hereinabove described, to thereby provide a self extinguishingcomposition which does not release hydrogen chloride into thesurrounding atmosphere.

The particle material may be either calcium carbonate or bariumcarbonate; calcium carbonate being preferred. Carbonates of sodium orpotassium are generally not suitable for these specific applications, inthat, although these compounds would prevent the evolution of hydrogenchloride into the surrounding atmosphere, their hygroscopic propertieswould have an adverse effect on the electrical properties of theinsulation or jacketing.

The particle material employed in the compositions of the instantinvention, for combining with the hydrogen chloride otherwise evolved atelevated temperatures, must have an average particle size no greaterthan 250 millimicrons and generally no greater than 100 millimicrons.More particularly the average particle size is of the order of 10 to 100millimicrons, although a range of 10 to 50 millimicrons and preferably,a range of 10 to 30 millimicrons, is preferred.

As previously indicated, such particle material is present in an amountwhich is at least sufficient to combine with essentially all of theevolved hydrogen chloride; i.e., the hydrogen chloride chloride evolvedin the smoke is less then 1.5% and more generally, less than 1.0%calculated on the basis of 1 kilogram of polymer. With smaller averageparticle sizes, such minimum amount approaches the calculatedstoichiometric amount.

The composition employed for forming insulation or jacketing forelectrical usage, also includes a plasticizer to provide desiredmechanical properties. Such plasticizer is generally present in anamount of from 30 parts to 80 parts per 100 parts of polymer, all byweight. The plasticizer component of the composition may be made up ofone or more compounds which are used with polyvinyl chloride orpolychloroprene; such plasticizers being preferably non-flammable toprovide a self-extinguishing composition.

The non-flammable plasticizer included in such compositions, ispreferably an aromatic phosphate, such as tricresyl phosphate, diphenylcresyl phosphate, dicresyl phenyl phosphate, triphenyl phosphate,trixylenyl phosphate, and mixtures thereof.

It is understood that mixed aliphatic-aromatic phosphates may also beemployed, such as diphenyl nonyl phosphate and the like. However, thesubstitution of an aliphatic group for an aromatic group reduces theoverall non-flammable properties of such plasticizers. The use of thespecified non-flammable plasticizers and others known in the art, isdeemed to be within the knowledge of those skilled in the art, takenwith the teachings herein.

In some cases, the plasticizer component of the composition may includea flammable plasticizer, in which case the composition may or may not beself-extinguishing. Such flammable plasticizers include phthalates suchas dioctyl phthalate, dinonyl phthalate, didecyl phthalate and mixturesthereof.

The preferred compositions for electrical applications, i.e. asinsulation and/or jacketing, preferably comprise polyvinyl chloride orpolychloroprene; a non-flammable plasticizer, preferably a tri-aromaticphosphate of the type hereinabove described; and calcium or bariumcarbonate, preferably calcium carbonate. The composition generally alsoincludes stabilizers, lubricants and other known components.

A particularly preferred composition is one which contains calciumcarbonate in an amount of 100 parts per 100 parts of polyvinyl chloride,preferably 120 parts of calcium carbonate per 100 parts of polyvinylchloride; with the calcium carbonate having an average particle size of50 millimicrons, and preferably 30 millimicrons or less.

The following examples are illustrative of the instant invention, butare not to be deemed in limitation thereof.

    __________________________________________________________________________    Examples                                                                                  1     2     3     4     5     6                                   __________________________________________________________________________    polyvinyl chloride                                                                        100   100   100   100   100   100                                 plasticizer A                                                                             50    63    63    35    35                                        plasticizer B                       30    70                                  milled chalk      60                                                          precipitated chalk      60    60    100   120                                 stabilizers 11    5     5     5     11    10                                  after burning time                                                            in seconds  5     13    60    0     0     0                                   % hydrogen chloride                                                                       100   60    21    20    0     0                                   evolved                                                                       __________________________________________________________________________

Plasticizer A is of the phthalate type such as diisooctyl phthalate,octyl phthalate, butyl octyl phthalate, and the like. Plasticizer B isof the aromatic phosphate type such as tricresyl phosphate, dicresylphenyl phosphate, and more particularly, as in Example 6 above, diphenylcresyl phosphate.

The milled chalk is of conventional type, having an average particlesize substantially greater then 250 millimicrons. The precipitated chalkhas an average particle size of about 50 millimicrons. The stabilizersare of the usual type found in polyvinyl chloride compositions, such asbarium-cadmium laurate complexes.

It will be apparent that in the case of Example 1, containing no chalk,the total hydrogen chloride is liberated when the composition issubjected to elevated temperatures sufficient to effect a decompositionof the polymer. The use of milled chalk, Example 2, gives some reductionin evolved hydrogen chloride.

However, when the milled chalk is replaced by precipitated chalk havingan average particle size of about 50 millimicrons, as in Examples 3-6;the evolved hydrogen chloride is materially reduced; and in Examples 5and 6, is reduced to zero, making such compositions acceptable forelectrical applications.

In another example 7, 100 parts of polyvinyl chloride was combined with70 parts of diphenyl cresyl phosphate, 120 parts of calcium carbonatehaving an average particle size of 30 millimicrons and 12 parts ofstabilizer of the barium-cadmium laurate complex type admixed with epoxycompounds. When this composition was subjected to elevated temperatures,released hydrogen chloride was less than 1% over a range of temperaturesup to 650° C; the percentages being calculated on the weight of polymerused.

In a further example 8, 100 parts of polyvinyl chloride was combinedwith 70 parts of diphenyl cresyl phosphate, 237 parts of bariumcarbonate having an average particle size of 70 millimicrons, and 12parts of stabilizer of the barium-cadmium laurate type admixed withepoxy compounds. When this composition was subjected to elevatedtemperatures in excess of 200° C, the released hydrogen chloride wasless than 1% calculated on the weight of polymer. In the foregoingexamples, the parts are by weight.

The compositions of the instant invention, where the particle matter isof very small average particle size and is present in amounts surpassingthe calculated stoichiometric amounts required; are particularlyapplicable for electrical usage. Thus, as shown in FIGS. 1, 2; anelectrical cable 10 comprises a conductor 11 of copper or aluminum andan insulating layer 12 therefor of normally plasticized polyvinylchloride or vulcanized rubber.

A sheath or jacket 13 is extruded over insulation 12, such jacket beingmade of a composition as set forth in Example 6. It is understood thatinsulation 12 may also be made of a polyvinyl chloride composition as inExamples 5 or 6.

A comparison of the properties of a conventional polyvinyl chloridejacket A, and a polyvinyl chloride jacket B made in accordance withExample 6, follows:

    ______________________________________                                                           A          B                                               ______________________________________                                        hydrogen chloride lost in                                                     smoke after 30 min. at                                                        650° C, using 50 liters/hr.                                                               201        1                                               of dry air, in grams/kg.                                                      polymer                                                                       hydrogen chloride lost in                                                     smoke after 30 min. at                                                        650 ° C, using moist air                                                                  215        1                                               with 8.7 g. water/cu. meter,                                                  in grams/kg. polymer                                                          Oxygen index %     23.3       27.7                                            ______________________________________                                    

It will be apparent that polymer compositions of the instant inventionhave a wide variety of applications, particularly because of the uniquecombination of self-extinguishing behaviour with a smoke free ofhydrogen chloride or ether deleterious acidic compounds.

While such compositions are of special interest as insulation andjacketings for electrical cables and conductors; these compositions arealso attractive for making floor tile, packaging and containers of allsorts, sheet plastic and film, laminates or avrious kinds, and moldedproducts generally.

I claim:
 1. In an article, comprising an electrical conductor, aninsulator and a jacket, the improvement comprising, at least one of saidjacket and insulator being formed from a member selected from the groupconsisting of polyvinyl chloride and polychloroprene, said member beingplasticized with a plasticizing amount of a non-flammable plasticizer,said member containing a material selected from the group consisting ofthe carbonates of calcium, barium, magnesium, strontium, sodium,potassium, lithium and mixtures thereof, said material having an averageparticle size which does not exceed 250 millimicrons and being presentin an amount which is at least sufficient to combine with essentiallythe entire amount of hydrogen chloride which is evolved at temperatureswhich occur in a fire to thereby prevent evolution into the surroundingatmosphere of the hydrogen chloride when the article is subjected tosaid temperatures.
 2. The article of claim 1 wherein said member ispolyvinyl chloride.
 3. The article of claim 2 wherein said material iscalcium carbonate.
 4. The article of claim 3 wherein the non-flammableplasticizer is an aromatic phosphate plasticizer.
 5. The article ofclaim 4 wherein the plasticizer is present in an amount from about 5parts to about 80 parts per hundred parts of the polymer, all by weight.6. The article of claim 1 wherein said member is polychloroprene.
 7. Thearticle of claim 6 wherein said material is calcium carbonate.
 8. Thearticle of claim 7 wherein the non-flammable plasticizer is an aromaticphosphate plasticizer.
 9. The article of claim 8 wherein the plasticizeris present in an amount from about 30 parts to about 80 parts perhundred parts of the polymer, all by weight.
 10. The article of claim 5wherein the jacket is formed from said member.